Cathode-ray deflection circuit



arch 8, i949.

Filed March 17, 1945 G. D. HULST, JR

CATHoDE-RAY DEFLECTION CIRCUIT 2 Sheets-Sheet l INVENOR.

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March 8, i949.. G. D. HULST, .JR 463,969

' CATHoDE-RAY'DEFLECTION CIRCUIT Filed March 17, 1945 24 Sheets-.Sheet 2 IN VEN TOR.

Hrmwfy AAAAAA AAAAA A VV AAAAA VVVVVV Patented Mar. 8, 1949 CATHODE-RAY DEFLECTION CIRCUIT George D. Hulst, Jr., Upper Montclair, N. J., assignor to Radio Corporation of America, a co1'- poration of Delaware Application March 17, 1945, Serial No. 583,255

9 Claims. 1

This application is a continuation-in-part of application Serial No. 568,084, led December 14, 1944, now Patent Number 2,432,158, in the names of George D. Hulst, Jr., Earl Schoenfeld and Garrard Mountjoy, and entitled Radio navigation systems.

My invention relates to cathode ray deflection circuits and particularly to circuits for producing a cathode ray trace having an expanded portion.

An object of the invention is to provide an improved means for producing a cathode ray trace having an expanded portion.

A further object of the invention is to provide an improved means for producing a deflecting voltage Wave having an initially steep slope iollowed by a more gradual slope.

By Way of example, one embodiment of the invention will be described as designated for producing a fast-sweep trace in a ra-dio navigation system such as that disclosed in Patent Number 2,445,361 in the names of Garrard Mountjoy, George D. Hulst, Jr., and Earl Schoenfeld, and entitled Radio navigation system.

In practicing the above-mentioned embodiment of the invention, a vacuum tube has two resistor-capacitor circuits, having different ltime constants, which are connected in series with each other in the cathode circuit of the tube.

The capacitors of these two circuits are charged by anode current flow through the vacuum tube. The dei-lecting voltage is produced by applying a pulse to the grid of the vacuum tube to drive it to plate current cut-off. During this cut-01T period the two capacitors discharge at -diierent rates through their shunting resistors, respectively, whereby the sum of the voltages across the two shunting resistors is a deflecting voltage of the desired wave form. In another embodiment of the invention a plurality of resistorcapacitor circuits having different time constants are charged through separate tubes.

The invention will be better understood from the following description taken in connection with the accompanying drawing in which Figure 1 is a block and circuit diagram of one embodiment of the invention,

Figure 2 is a circuit diagram of a second embodiment of the invention, and

Figures 3 and 4 are groups of graphs that are referred to in explaining the operation of the circuit shown in Fig. 2.

Referring to Fig. 1, the deflecting wave producing circuit comprises a vacuum tube I0 having an anode II, a control grid I2 and a cathode I3. Ihe anode I! has a direct-current voltage applied thereto through an anode resistor I4. The grid I2 has periodically recurring negative voltage pulses I6 and I1 applied thereto through a coupling capacitor I5, these pulses driving the (Cl. Z50-27) tube I0 periodically to anode current cut-off. A grid leak resistor is shown at I8.

Between the cathode I3 and ground there are connected a resistor-capacitor circuit 2| comprising a resistor ZIa and a capacitor 2 Ib, and a resistor-capacitor circuit 22 comprising a resistor 22a and a capacitor 22h. As shown by the sample circuit values on the drawing, given in ohms, microfarads and micro-microfarads, the circuit 2| has a faster time constant than the circuit 22.

An integrating or delay circuit 23 is connected to receive the voltage from across the circuit 2| and supply it to a voltage divider resistor 24 having a variable tap 26 thereon. The resistor 24 is connected across the resistor-capacitor circuits 2| and 22 by way of the delay circuit 23 and ground. The delay circuit 23 comprises a plurality of sections connected in cascade, each section consisting of a series resistor and a shunt capacitor, values for which are given on the drawing in ohms and micro-microfarads, merely by way of example.

The deflecting voltage waves resulting from the application of pulses I6 and I1 to the grid I2 are shown by the graph 3|. The useful deflecting portion of the wave lies between the points a and b, while the resetting or capacitor recharging portion of the wave lies between the points b and c.

Referring now to the circuit that produces the pulses I6 and I1, there is shown, by `way of example, an Eccles-Jordan oscillator 33 that produces a square wave 34 in a xed time relation to triggering or timing pulses supplied over a lead 36. The wave 34 is applied to a multivibrator 31 to produce a rectangular Wave 38. The timing of the back edge of the narrow pulse portion of wave 38 is adjustable by means of a knob 39 which may, for example, vary the positive bias on the grid of a multivibrator tube as is well understood in the art.

The waves 34 and 38 are applied to diierentiating circuits 4I and 42 to produce the waves 43 and 44, respectively, consisting of positive and negative pulses. The Waves 43 and 44 are passed through clipping circuits 46 and 41 to produce the waves 48 and 49, respectively, each comprising pulses of one polarity only. The waves 48 and 49 are supplied to a mixer tube or circuit 5f which supplies to the grid I2 the combined waves 48 and 49 as the negative pulses I6 and I1.

The resulting deflecting wave appearing at the tap 26 is amplied by a suitable amplifier 52 and applied to the deecting plates 53 of a cathode ray tube 54 whereby the desired expanded trace -56 is obtained. The expansion at the left end of the trace 56 is apparent from the Wider spacing of the timing marks indicated at 51, the

marks 51 being produced by applying timing pulses of a certain repetition rate to the vertical deilecting plates 58. The source of such timing pulses maycomprise a crystal oscillator followed by a chain of frequency dividers (not shown) and may be the same source that supplies triggering pulses to the E-J oscillator 33.

Referring more specically to the way in which the deflecting wave shown by graph 3i is ,roduced, during the time the'tube Hi is held at cutoff by a pulse I6 or I1, the capacitors ib and discharge through resistors 2id and 23a, respectively. The time constant of the circuit 2i is short compared with the cut-off period while that of the circuit 22 preferably is long compared with Vthe cut-offperiod. After the rounding off of the corner of the wave 3| and the resulting slight delay, 'indicated by the legend, the wave has a steeply sloping portion a-,zc produced by the fast 'capacitor discharge in the counter 2i, and then amore gradually sloping portion --b produced by the slower capacitor discharge in the circuit 22. Thus, there is produced the desired deflecting wave portion a-b that produces the expanded cathode ray trace whereby timing marks, for example, at the left end ci the trace maybe counted more accurately. In the example given, the wave portion a-b is approximately logarithmic in wave form.

For some applications of the invention the delay at the start of the defiecting wave portion a-b may be unnecessary or undesirable, in which -case the delay network 23 is omitted and the resistor 24 is connected directly across the circuits 2| and 22.

Fig. 2 shows another embodiment of the invention in which resistor-capacitor circuits of different time constants are charged through separate vacuum tubes. This particular circuit with the circuit values indicated on the drawing is designed to provide a slow sweep trace having an expanded portion for use in a radio navigation system, for example, where timing marks are to appear on the trace. This embodiment of the invention is described in Patent Number 2,432,158 in the names of George D. Hulst, Jr., Eari Schoenfeld and Garrard Mountjoy, and entitled Radio navigation systems.

Referring to Figs. 2 and a, an Eccles-Jordan oscillator 65 supplies a square wave voltage C through a diierentiating circuit E35 to a multivibrator which comprises two triodes |32 and |33 that'are connected to form a cathode-coupled multivibrator. The resulting pulses D produced by the diierentiating circuit are applied to the grid of the triode |32, this grid having an adjustable positive bias applied thereto from apotentiometer resistor |62 through a resistor |34. This bias is adjusted by means of the control knob |02 for adjusting the time of occurrence of the back edge of the narrow multivibrator pulse of the wave E. The differentiating circuit |66 comprises a small coupling capacitor |36 and the grid resistor i3d.

A wave C is also obtained from the E J oscillator 65, this wave being the same as the wave C .but of opposite polarity. The wave C is supplied to a differentiating circuit |31 to obtain the vpulses D.

The differentiating `circuit |31 supplies vthe pulses D to the grid of a triode H3A that yforms part of a mixing circuit lil. The differentiating `circuit |01 comprises a small coupling capacitor |31 and a grid resistor |38. A differentiating cir- .cuit |08 .applies the .pulses IEP' to the grid of -a r triode HilB forming the other part of the mixer H6, the tubes H3A and lldB having a common cathode resistor |39 across which the mixed signalsD and-l?1 appear. The differentiating circuit IEB comprises a small coupling capacitor |li| and a grid resistor |42.

The mixed signals D' and F preferably are applied through a clipper diode |43 to keep the amplitude of the positive pulses a constant value. The clipped pulses are applied to the grids of a pair of triodes |44 and |46.

The triodes |44 and |656 have wave shaping cathode circuits |41 and Hi8, respectively. The circuit |41 comprises a cathode resistor M3 and a capacitor |5| in parallel therewith. The circuit Id?, comprises a cathode resistor 52 and a capacitor |53 in parallel therewith.

Upon the occurence of either a pulse D or a pulse F, the tubes IMS and M6, which are Ynormally biased to cut-off, conduct anode .current yto charge the capacitors |5| and lrespectively, This Vcharging Voi |5| and |53 is .practicaliy iinstantaneous. At the termination of the pulse D' or F, the capacitors |5| and 'E53 discharge ata rate that is slow compared with the charging'rate and at a rate that is determined by theitime `constants of the circuits |41 and M8, thesetime constants differing from each other. Thus, as-illustrated in Fig. 3, across the circuits y|111 and ld there are produced the voltage waves :rand y, respectively, which are to be combined withza third voltage wave e to produce the desired logarithmic deflecting wave G.

The wave a is obtained by applying the .pulses D and .F from the cathode yresistor |33 over a conductor |53 to the grid of a tube ii'whichincludes a wave shaping network |51 in its cathode circuit. The network 15'? comprises a'high impedance resistor |53, the lower portion of'a biasing resistor |59, and a capacitor iti-i. As in the wave shaping circuits for producing the waves .':c and y, the capacitor itil is charged rapidly upon application of a pulse to the tube |55. Toproduce Wave e, however, the discharge of vcapacitor i6! is made slow enough by properadjustment of the time constant of network |51 so that `it (unlike capacitors |5| vand |53) has not discharged completely by the time the next pulse D or F occurs. The wave a is applied to a cathode follower tube |53.

It will be seen that the effect of adding the waves a: andy to the wave .e is togreatly increase the slope of the deflecting wave 1G at its start whereby the scale for the corresponding portion of the cathode-raytrace isexpanded. The waves y and e are added by supplying vthem through leads |62, |623 and idd to the input circuit of the deiiecting-wave amplier H3. The leads ld preferably include 'high impedance Yresistors |66 and |61 shunted by capacitors land |53, respectively, for obtaining `undistorted addition of the' several waves. It will be apparent that the deecting wave G may beshaped asdesired for different scale expansions by changing .the time constants of one or more of the-circuits m1,

|48 and |51.

In Fig. 2, the circuit values have been yindicated in ohms, thousands of ohms, megohms, ymicrofarads and micro-microfarads merely by way of example.

I claim as myfinvention:

1. `In combination a plurality .of resistorcapacitor circuits each comprising a capacitor shunted by ya resistor .and having different .time constants, means for supplying direct current .to

said circuits for charging the capacitors therein, means for interrupting periodically the flow oi charging current to said circuits whereby each of said capacitors discharges through its shunting resistor at a certain rate during each charging current interruption, means for adding the voltages appearing across said resistors to obtain a periodically recurring delecting voltage having a Wave form of decreasing slope, and means for supplying said added voltages to a utilization circuit.

2. In combination a plurality of resistorcapacitor circuits each comprising a capacitor shunted by a resistor and having diierent time constants, means for supplying direct current to circuits for charging the capacitors therein, means for interrupting periodically and sub'- stantially simultaneously the flow of charging current to said circuits whereby each of said capacitors discharges through its shunting resistor during each charging current interruption at a rate determined by the time constant of said discharging circuit, means for adding the voltages appearing across said resistors t0 obtain a periodically recurring deecting voltage having a wave form of decreasing slope, and means for supplying said added voltages to a utilization circuit.

3. A cathode-ray deflection wave circuit comprising a vacuum tube having an anode, a cathode and a control grid, a plurality of resistor-capacitor circuits having diierent time constants and connected in series with each other, said series connected circuits being connected in series with the cathode-anode impedance of said tube, means for supplying direct-current to said circuits for charging the capacitors therein to a predetermined direct-current potential, and means for interrupting periodically the flow of charging current to said circuits, and means for applying the sum of the voltages that appear across said circuits during said periods of current interruption to a utilization circuit.

4. A cathode-ray deflection wave circuit comprising a vacuum tube having an anode, a cathode and a control grid, a plurality of resistor-capacitor circuits having different time constants and connected in series with each other, said series connected circuits being connected in series with the cathode-anode impedance of said tube, means for charging the capacitors of said circuits to a predetermined direct-current potential including means for charging at least one of said capacitors through said cathode-anode impedance, and means for interrupting periodically the flow of charging current to said capacitors including means for applying to said grid periodically recurring negative pulses of sufficient amplitude to drive said tube periodically to anode current cutoff, and means for applying the sum of the voltages that appear across said circuits during said periods of current interruption to a utilization circuit.

5. A cathode-ray deection wave circuit comprising a vacuum tube having an anode, a cathode and a control grid, a plurality of resistor-capacitor circuits having di'erent time constants and connected in series with each other, said series connected circuits being connected in series with the cathode-anode impedance of said tube, means for charging the capacitors of said circuits to a predetermined direct-current potential through said cathode-anode impedance, and means for applying to said grid periodically recurring negative pulses of sucient amplitude to drive said tube periodically to anode current cut-off, and means for applying the voltage that appears across said circuits during said cut-oir periods to a utilization circuit.

6. A cathode-ray deflection Wave circuit comprising a plurality of vacuum tubes each having an anode, a cathode and a control grid, a pluraity ci resistor-capacitor circuits having differ-- ent time constants and connected in the cathode lrcuits of said tubes, respectively, each resistorcapacitor circuit comprising a capacitor shunted by a resistor, means including said vacuum tubes for charging the capacitors in the respective cathode circuits of said tubes to a predetermined direct-current potential through the respective cathode-anode impedances of said tubes, and means for applying to said grids periodically recurring negative pulses of sufcient amplitude to drive said tubes periodically to anode current cutci whereby said capacitors discharge through their shunting resistors during said cut-oi periods, and means for applying the sum of the voltages that appear across said circuits during said cut-oir periods to a utilization circuit.

7. In combination a plurality of resistorcapacitor circuits each comprising a capacitor shunted by a resistor and having different time constants, means for supplying direct current to said circuits for charging the capacitors therein, means for interrupting periodically the flow of charging current to said circuits whereby each of said capacitors discharges through its shunting resistor at a certain rate during each charging current interruption, means comprising a resistorcapacitor delay network for delaying the voltage appearing across the resistor-capacitor circuit having the faster time constant, and means for adding the voltages appearing across said resistors to `obtain a periodically recurring deflecting voltage having a wave form of decreasing slope.

8. The invention according to claim 4 wherein the time constant of one of said resistor-capacitor circuits is short -compared with said period of anode current cut-01T and wherein the time constant of another of said resistor-capacitor circuits is long compared with said period of anode current cut-off.

9. The invention according to claim 5 wherein the time constant of one of said resistor-capacitor circuits is short compared with said period of anode current cut-01T and wherein the time constant of another of said resistor-capacitor circuits is long compared with said period of anode current cut-01T.

GEORGE D. HULST, JR.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number 

